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C. H. CHANDLER.

LEAD PLATING.

APPLICATION FILED MAR. 21. 1918.

Patented Nov. 18, 1919.

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LEAD-PLATING.

Specification of ibettcrs Patent. 1 Patented Nov. 18, 1919.

Application filed inch 21,1918. Serial No. 223,817.

. or objects subject in their usage to rust or corrosion.

As illustrative of the practice of my 1nven'tion I shall discuss the lead plating of torpedo air flasks as a speclfic instance of great immediacy of practical importance.

In plating such an-ob ect as a torpedo air flask it is of great importance that the lining be a smooth tough non-corrodible Skin so perfectly united to the flask wall that it will not be ruptured or dislodged by expansion or contraction of the vessel either by changes of pressure or temperature.

Furthermore, it is of great practlcal 1mportanoe to be able to line large vessels or coat other extensive surfaces rapldly and at a minimum of labor and expense.

In accordance with my invention I am able to deposit electrolytically a hard homogeneous coating of .lead very rapidly and economically.

In practising-my invention I preferably make an electrolyte by building up a solution 'of lead carbonate or white lead in hydrofluosilicic acid with a small amount of gelatin or glue. The electrolyte should contain at least 8% of lead and the free acid should be under 5%. These percenta es may vary slightly but it is to be noted at should the lead fall below 5% a dark slimy deposit is formed. The gelatin should be added to about 1 per cent. with which the lead deposits in a smooth and solid coating of specific gravity 11.40, the tensile strengt being considerably greater than lead in its ordinary form.

In the accompanying drawings, I have illustrated apparatus for the practice of my invention.

Figure 1 is a transverse section of a torpedo air'flask that is being coated according to my method, and

Fig. 2 is a partial longitudinal, section thereof.

In practising my invention the air flask with one'head ground on is entirely freed l on its inner surface from grease or forei \matter and filled with the electrolyte 2, in

any suitable manner.

The flask is connected preferably at several points so as to form the cathode. The

electrical connections are indicated at 3.

The anode 4 for such a flask is preferably prepared by casting, in a cylindrical or other convenient form. This may be of pure lead or may be of some suitable alloy if a coating other than of pure lead is deslred.

The anode should be supported out of contact wlth the flask and should be immersed n the electrolyte-and is suitably connected in the circuit, as indicated at 5. The feed Wires '3 and 5 are connected with the respective poles of any suitable electric energlzer (not shown).

With a pure lead anode as described with an electrolyte containing 10.5% lead and 3%% free acid, I have been able to deposlt lead coatings, indicated generally at 6, at the rate of 3.847 grams per ampere hour or 4.? ampere days per pound. The current denslty being from 12 to 20 amperes per square foot vof surface. The castlng of the lead anodes is a very lnenpenslve and convenient form of preparlng the anode and supplying the lead. The qualltiespf lead transported by current are comparatlvely large so that only a relatively small amount of power is necessary, the lead having very favorable physical and electrochemical constant for deposition.

Lead coatings deposited in this manner cover the steel completely and are most tenaeious, being only removable by digging off with a sharp instrument. It resists severe treatment such as brushin with a steel brush, and the coatin' remams smooth and umform through conslderable degrees of expansion and contraction of the flask, and is a most effective preventive against the usual corros1ve efi'ects.

My invention-as set forth is capable of a variety of modifications and a variety of usages, all without departing from the spirit and such modifications are to be construed as. within my invention if within the limits defined by the appended claims.

What I therefore claim and desire to secure by Letters Patent is:

1. The method of lining a torpedo flask l tically depositing on it as a cathode a thin (l ense leaden coating internally thereof from an electrolyte from a lead salt of hydrofluosilicic acid contained within the flask.

2. The method of lining a torpedo flask or the like, consistin in filling said flask shell with an electro yte containing a lead salt of hydrofluosilicic acid in the pro ortions of substantially 8% lead and by rofluosilicic acid not exceeding 5% free, connecting said flask shell as a cathode and in suspending in said contained electrode and out of contact with said flask shell a lead anode and in assing a current therethrou h.

3. The met 0d of coating a metallic ha y, consisting in gradually electrolytically depositing on it as a cathode a dense leaden or the like, consisting in gradually electroskin from an electrolyte consisting of a lead salt of hydrofluosilicic acid. 4. The process of depositing a lead coating on the surface of a metal object consisting in formin an electrolyte containing a lead salt of hy rofluosilicic acid having sub- Stitlltlilll? 8% lead and less than 5% free acid an substantially .1% gelatin, and in exposing a leaden anode and the surface to be coated in said electrolyte in anode and cathode relation.

In testimony whereof I aflix my signature in presence of two witnesses.

Emma Bnn'r Comma. 

